Speaking from my experience, Iberostar is your best bet, especially the Bavaro Suites. Iberostar has 3 hotels at that location, Bavaro being the better however, you get rights to the other two hotels. Iberostar is also next to the RIU, which has five hotels now. Secrets is nice for romantics, but it is generally off by itself. Melia is very nice too. Haven't been to Palladium. Remember, reviews you read were from others who may, or may not, share your ideas of a nice vacation. Plus, the majority of people that actually write reviews are people who unfortunately did not experienced a good time and want to vent.
Not sure what your exactly looking for in your vacation, but PC is not a party place that you would traditionally see with places like Cancun or Playa de Carmen. PC is mostly made up of AI's with no "downtown" action. The action your going to get is typically that of your resort, many of which have several bars or lounges. You can wander outside, but that's limited as well and not near as much to do as in other locations like PP or Sousa, as one of the previous respondant's indicated. Also, fall is low travel season, so there will not be the crowds you may think.
What you will get at PC is some of the most beautiful beaches and a relaxing time.
Hope this kinda helps.
Brian.